1. Field of the Invention
The present invention relates to a method of extracting a region of a specific configuration, a method of extracting a specific region, and a method of determining copy conditions, and in particular, to a method of extracting a region of a specific configuration for extracting a region of a specific contour configuration from an image, and to a method of extracting a specific region for extracting from an image a specific region having a predetermined characteristic, and to a method of determining copy conditions for determining copy conditions by using the aforementioned methods of extracting.
2. Description of the Related Art
When a photograph of a person is viewed, the region which is most noticed is the person's face. When, for example, an original image recorded on a film or the like is to be printed onto a copy material such as photographic printing paper, the exposure amounts must be determined such that the color of the person's face is printed at an appropriate color.
Therefore, conventionally, a film image is divided into a plurality of regions which have been fixedly determined in advance, on the basis of the empirical principle that in a photograph of a person, there is a high probability that the person will be positioned in the substantially central portion of the image. The respective regions are weighted, with the weights of the regions positioned In the substantially central portion of the image being the greatest. Weighted average values of the transmission densities of the three colors of each of the regions are determined, and the exposure amounts are determined on the basis of the weighted average values.
In the above-described method, if a person actually is positioned in a vicinity of the substantially central portion of the image, exposure amounts for printing the person appropriately can be obtained. However, a drawback arises in that in a case in which the person is positioned at a position which is distant from the central portion of the image, the proper exposure amounts cannot be obtained. Further, for images in which it is easy for density failure or color failure to occur, as in the case of images photographed by using an electronic flash or images in which a backlit scene is photographed or the like, a drawback arises in that it is difficult to obtain the appropriate exposure amounts.
The applicants of the present application have proposed the following method of determining exposure amounts in Japanese Patent Application Laid-Open (JP-A) No. 4-346332. A color original image is divided into a plurality of pixels, and each pixel is divided into three colors of R, G, B and photometrically measured. A histogram for the hue values (and the saturation values) is determined on the basis of the photometric data. The histogram is divided per mountain, and for each pixel, a determination is made as to which of the divisional mountains the pixel belongs. The pixels are divided into groups corresponding to the divisional mountains. The color original image is divided into a plurality of regions per group (so-called clustering). Among the plurality of regions, a region is, assumed to correspond to the face of a person, and the exposure amounts are determined on the basis of the photometric data of the region assumed to be a person's face.
Further, Japanese Patent Application Laid-Open (JP-A) No. 6-160993 discloses the following method by which the probability of extracting a region corresponding to a person's face is increased. The regions contacting the outer edge of the image are Judged to be background regions and are excluded. An extracted region is diagramed, and on the basis of the configuration of the extracted region and the configurations of the neighboring regions positioned at the periphery of the extracted region, a determination is made as to whether the extracted region is a region corresponding to a person's face.
However, there may be for example flesh-colored regions such as ground, tree trunks, or the like in the original image, and the hue and saturation of such flesh-colored regions may approximate the hue and saturation of a region corresponding to a person's face In the image. In such cases, with the above-described methods, such a region may be mistakenly judged to be a region corresponding to a person's face. Further, when such a flesh-colored region is adjacent to a region corresponding to a person's face, there are cases in which the flesh-colored region and the region corresponding to the person's face cannot be separated and the original image cannot be divided into regions of proper ranges. In the above-described conventional art, processing is carried out on the premise that one of the divisional regions is a region corresponding to a person's face. Therefore, in a case in which the original image cannot be divided into regions of proper ranges, a drawback arises in that a region corresponding to a person's face will be judged mistakenly, and exposure amounts enabling proper printing of the person's face cannot be obtained.
As one method of properly extracting a predetermined region from an image without receiving effects from the color or the like of adjacent regions, edges (points where the change in density or luminance is great) in the image are detected, and for each detected edge, the determination as to whether there exists another edge in the periphery of that edge is repeated so that a plurality of contour lines, which are respectively formed by edges running together in a row, are extracted. For each of the extracted contour lines, a process such as pattern matching with the contour configuration of the predetermined region is carried out, and a determination is made as to whether the contour line is a contour line which corresponds to the contour of the predetermined region. The predetermined region is extracted in this way. Because the contour of a region corresponding to a person's face is substantially elliptical, in the above-described method, it is possible to extract a region assumed to correspond to a person's face by determining, from among the plurality of extracted contour lines, a contour line which corresponds to the contour of a substantially elliptical region.
However, processing for extracting a plurality of contour lines from an image and processing for determining, from among the plurality of extracted contour lines, a contour line corresponding to the contour of a predetermined region which is to be extracted are extremely complicated. A drawback arises in that when a region corresponding to a person's face or the like is to be extracted from an image by using the above-described method, processing requires an extremely long time.